Measuring Instruments — Compass Series

4074 Metal Compass

Keywords: Metal Compass, Prismatic Compass, Military Compass, Lensatic Compass, Compass with Clinometer

Precision Bearings, Map Work, and Field Calculations in One Metal Compass.

The 4074 is a rugged metal prismatic compass built for serious field navigation. A 360° pivoting dial and reading prism let you take precise bearings and marching directions, while an integrated clinometer measures slope and height differences. Distance-measuring notches on the glass and a full set of built-in calculation tables make it possible to work out distance, height, and position directly in the field — no separate tools required.

Key Components

1.  Graduated metric scale

2.  360° pivoting dial

3.  Wind rose

4.  North line with north arrow

5.  Glass

6.  Distance-measuring notches

7.  Aiming line

8.  Cover

9.  Case

10.  Hinge

11.  Reading lens or prism

12.  Holding ring

13.  Level bubble

14.  Thread and tripod mount

15.  Central support

16.  Reading adjustable eyepiece

17.  Clinometer

Core Functions

1.  Reading Marching Direction — Sight an object through the notch, aiming line, and reading lens or prism; the value on the wind rose gives the marching direction and azimuth of the object.

2.  Following a Set Direction — With a known marching direction, look through the reading system and turn until that value appears on the graduated scale, then walk that heading.

3.  Map Orientation — Align the centimeter-marked edge with the nearest meridian on the map, then rotate the map until the north-seeking needle lines up with the notch on the glass — the map is now correctly oriented to the ground.

4.  Plotting a Marching Direction on the Map — Draw a line from your position to your destination, align the compass edge to that line, then read and follow the resulting marching direction to your target — repeating with auxiliary points for longer routes.

5.  Position Fixing on the Map — Take bearings on two well-visible points from your location, plot both lines on the oriented map, and the intersection marks your position.

6.  Using the Clinometer — Release the pendulum, aim at the upper or lower edge of the target through the reading lens, and read the slope or height difference in degrees or percent once the pendulum settles.

7.  Measuring Distance on the Ground — Measure the angle between two points using the compass, then apply the built-in calculation table to convert that angle into a ground distance.

8.  Measuring the Height of an Object — Read the inclination in degrees or percent with the clinometer, then use the table's pendence and height/distance columns together with the known distance to calculate the object's height.

9.  Measuring Distance from a Known Height or Width — Invert the same calculation: with an object's height or width already known, the measured angle gives you the distance to that object.

10.  Measuring Distance with the Scale-Marked Glass — Count the notches between two targets on the glass's horizontal measuring line (each notch equals 10 units), then divide the known distance between the two targets by that unit count and multiply by 1000 to find the distance to the observer.

Table for Calculations

Use this reference table with the clinometer and compass readings to convert between angle units and to calculate pendence (slope %) and height-to-distance ratio in the field.

I Angle 0–360	II Angle 0–6400	III Angle 0–400	IV Pendence %	V Height/Distance
1	18	1	2	1/6
2	35	2	3	1/30
3	53	3	5	1/20
4	71	4	7	2/30
5	89	5	9	7/80
6	107	6	10	1/10
7	125	7	12	1/8
8	142	8	15	1/7
10	178	9	18	1/6
12	219	11	21	1/5
14	250	13	25	1/4
17	302	16	30	3/10
18	320	19	33	1/3
20	355	20	36	3/8
22	391	25	40	2/5
24	426	27	45	4/9
27	480	30	50	1/2
31	551	35	60	3/5
34	604	38	66	2/3
35	622	39	70	7/10
37	658	41	75	3/4
40	711	45	84	5/6
42	747	47	90	9/10
45	800	50	100	1/1
50	889	56	120	1+1/5

Applications

The 4074 metal compass is suited for land navigation and field survey work, including military and tactical use, orienteering, forestry and geology fieldwork, land surveying, and general outdoor navigation where accurate bearings, map orientation, and distance or height calculations are needed.